Fuel tank vapor recovery control

ABSTRACT

Vapors from the gasoline tank of a motor vehicle are connected by a line to the engine intake manifold to be burned. The line contains a fuel-air mixing valve that is opened by fuel tank vapor pressure to add air in the correct proportion to the fuel vapors so that the overall air-fuel ratio in the engine is unaffected by the addition of more fuel. A vacuum override to shut the valve is provided to prevent excessive idle speed r.p.m. increase.

United States Patent lnventor Kazimieras Kizlauskas Southfield, Mich.

Appl. No. 756,781

Filed Sept. 3, 1968 Patented Mar. 30, 1971 Assignee Ford Motor Company Dearborn, Mich.

FUEL TANK VAPOR RECOVERY CONTROL 7 Claims, 2 Drawing Figs.

US. Cl. 261/43, 261/72, 123/136 Int. Cl ..F02m 37/02 Field of Search 261 /72, 43

(Vented Bowl); 123/121, 136

[56] References Cited UNITED STATES PATENTS 1,948,135 2/1934 Sands 261/V.B. 2,029,142 1/1936 Wemhoner 261/72 3,001,519 9/1961 Dietrich et a1. 123/136 3,172,348 3/1965 Berg 26l/72UX Primary ExaminerTim R. Miles Att0rneys-John R. Faulkner and Robert E. McCollum ABSTRACT: Vapors from the gasoline tank of a motor vehicle are connected by a line to the engine intake manifold to be burned. The line contains a fuel-air mixing valve that is opened by fuel tank vapor pressure to add air in the correct proportion to the fuel vapors so that the overall air-fuel ratio in the engine is unaffected by the addition of more fuel. A vacuum override to shut the valve is provided to prevent excessive idle speed rpm increase.

FUEL TANK VAPOR RECOVERY CONTROL This invention relates, in general, to a motor vehicle engine fuel vapor recovery system. More particularly, it relates to the construction of a fuehair mixing valve for use in such a system.

From an antismog standpoint, it is desirable that fuel vapors that are emitted from a motor vehicle gasoline tank during a hot soak cycle not be freely ejected into the atmosphere, but be passed into the intake manifold of the engine to be subsequently burned. Considerable changes in the ambient temperature, however, may produce and force a large amount of fuel vapors from a full fuel tank or reservoir. Such a large additional quantity of fuel supplied directly to the carburetor or intake manifold generally will not burn properly in the absence of additional air.

Accordingly, the invention relates to-a valve located in the lines between a fuel tank or reservoir and the engine intake manifold for properly proportioning the amount of air to be mixed with the fuel vapors forced into the manifold. As a result, the overall carburetor fuel-air ratio is unaffected by the addition of vaporized fuel from the fuel tank.

It is a primary object of the invention, therefore, to provide a fuel-air mixing valve for a motor vehicle fuel vapor recovery system.

It is another object of the invention to provide a fuel vapor recovery system with a fuel-air mixing valve that is movable upon the attainment of a predetermined fuel vapor pressure to a position in which air is added to the fuel vapor and the mix ture is then admitted to the intake manifold of the engine.

It is a still further object of the invention to provide a valve of the type described above in which the valve is normally biased to a position blocking the flow of additional air and fuel vapor to the intake manifold; and, when once moved to an operative position, is moved to a different inoperative position blocking theflow of air and fuel whenever the engine idle speed vacuum increases to a predetermined level.

Other objects, features, and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustratinga preferred embodiment thereof, wherein:

FIG. 1 illustrates, schematically, an internal combustion engine fuel vapor recovery system; and,

FIG. 2 shows an enlarged cross-sectional view of the air-fuel mixing valve of FIG. 1.

FIG. 1 shows an internal combustion engine 10. It includes a cylinder block and crankcase 12 on which is mounted an intake manifold illustrated schematically at 14. Secured on the manifold is a conventional downdraft type carburetor having the usual main fuel-air mixture induction passage 16 containing a venturi 18. Flow through passage 16 is controlled by a pivotally mounted throttle valve 20. A known type of dry element air cleaner 22 covers the fresh air inlet to induction passage 16.

The carburetor in this case has a float bowl or fuel reservoir 24 that receives a supply of fuel through conduit means, not shown, from a fuel tank or reservoir 26, in a known manner. The fuel tank consists of a suitable container connected to an overflow tank indicated in general at 30. A fuel filler pipe 32 is closed by a cap 34, and has an overflow connection 36 joined to the overflow tank.

In the vapor recovery system illustrated, the fuel vapors from tank 26 are adapted to be directed to the intake manifold 14 of engine to be subsequently burned in the engine combustion chambers and thus be converted to less harmful forms before being passed into the atmosphere. As stated previously, in order to assure that the addition of fuel vapors to the manifold from the tank does not affect the overall fuel-air ratio in the carburetor, the fuel tank vapors are routed to the intake manifold through a fuel-air proportioning valve means 40.

As best seen in FIG. 2, valve means 40 includes a valve body 42 having a bore 44 in which is slidably mounted a spool valve 46. The latter has spaced lands 48, 50 and 52 connected by neck portions 54 and 56 of reduced diameter forming annular fluid chambers 58 and 60, respectively. The right-hand portion of the valve bore has a reduced diameter 62 that defines an annular fuel vapor pressure chamber 64. It also defines a shoulder 66 constituting a stop for the rightward movement of valve 46. The valve is biased against the stop by a spring 68.

The fuel vapor overflow tank 30 is connected by a line 70 (also see FIG. 1) to the valve bore 44 where it is blocked from further flow by the closed position of valve 46 shown. A branch line 72 is connected to chamber 64 so as to act on the right-hand end of the valve, in a manner to be described. The valve bore 44 is also connected to a supply of fresh air through a conduit 74 having an apertured air inlet or breather cap 76. The opposite portion of the valve body is provided with two outlet lines 77 and 78 that are interconnected to a common line 80. Lines 77 and 78, which are normally blocked in the closed position shown of the valve 46, cooperate respectively with the fresh air line 74 and fuel vapor line 70 when valve 46 moves from the position shown, as will be described more clearly later. Both lines 74 and 70 contain flow restricting orifices 82 and 84 each of a size calibrated to provide the proper ratio mixture of air and fuel in line when valve 46 is moved to the left to interconnect lines 74 and 77, and 70 and 78.

The valve body is further provided with a line 86 opening into the chamber'88 defined between the end land 48 of the valve and the valve bore 44. Chamber 88 is connected at its opposite end (FIG. 1) to the carburetor induction passage 16 at a location below the closed throttle position of throttle valve 20. This is so the intake manifold vacuum will act at all times on the valve land 48 for a purpose to be described.

The operation of the invention is believed to be clear from the above description and a consideration of the drawings. Briefly summarizing, however, when engine 10 is not operating, evaporation of fuel occurs in tank 26 if increase in ambient temperature occurs. This causes an increase in the pressure in tank 26 and an overflow into tank 30. Upon continued increase in temperature, the increase pressure in the overflow tank will act through line 70 in chamber 64 behind valve 46. With the engine at rest, no vacuum will exist in chamber 88 so that the force of spring 68 will be sufficient to maintain valve 46 in the position shown blocking the flow of fuel vapors or air into line 80.

Assume now that the engine is started and that vacuum is existing in chamber 88 as well as in line 80. The spring 68 is so calibrated or chosen that with low idle r.p.m. low vacuums, the spring will keep valve 46 closed until the fuel vapor pres sure in chamber 64 on the opposite end of valve 46 reaches approximately one-half p.s.i. Then any further increase will move valve 46 to the left to open both fuel vapor line 70 and air line 74 to the outlet line 80. The two orifices 82 and 84 will correctly proportion the amount of air and fuel added to the intake manifold.

As a result of the increased or additional fuel supplied to the intake manifold by way of line 80, the engine idle r.p.m. will increase. This will also increase the vacuum in the intake manifold. When the point is reached where the increased vacuum together with the force of the fuel vapor pressure in chamber 64 is sufficient to overcome the force of spring 68, valve 46 will be pushed by the fuel vapor pressure to a further inoperative position, to the extreme left against the stop 90. This blocks the further flow of fuel vapor and air to line 80 and into the intake manifold. Accordingly, no further increase in engine r.p.m. will occur at this time. In fact, without additional fuel, the idle speed will drop.

In actuality, the mixing valve will seek an equilibrium position between fully open and closed positions, to regulate the quantity of additional air-fuel mixture to be added so as to continue supplying fuel vapor and air so long as the desired maximum idle rpm. is not exceeded, assuming the fuel vapor remains the same. However, as additional fuel is added, the

'fuel tank vapor pressure should decrease so that eventually the valve 46 will close because the tank vapor pressure is below one-half p.s.i. The tank pressure will not, as a rule, ever rise enoughto itself move valve 46 against stop 90.

From the foregoing, therefore, it will be seen that the invention provides a complete metered burning of evaporated fuel in the combustion chambers of the engine; and that, therefore, there is no emission of raw fuel vapors into the atmosphere. It will also be seen that the invention provides a fuel vapor recovery system in which the overall engine fuel-air ratio is unaffected by the addition of evaporated fuel.

While the invention has been illustrated in its preferred em bodiment, it will be clear to those skilled in the arts to which it pertains they many changes and modifications may be made thereto without departing from the scope of the invention.

lclaim:

l. A fuel vapor emission control for use with an internal combustion engine having an intake manifold providing a variable source of vacuum, a carburetor having a fuel-air induction passage and a throttle valve rotatably mounted therein to control flow therethrough, a fuel reservoir having a fuel vapor area therein, said emission control comprising, a conduit means connecting the fuel vapor area to said vacuum at a point below said throttle valve, a' source of air connected to said conduit means, and fuel-air proportioning valve means in said conduit means controlling the flow of fuel vapor and air therethrough, said valve means including-a reciprocable valve spring-biased to an off position blocking flow of both fuel and air therepast, and variably movable therefrom by fuel vapor pressure above a predetermined level acting on one end of said valve to an on position connecting the vacuum to said air and fuel vapor.

2. A control as in claim 1, including additional means connecting said vacuum to said valve to act thereon and above a predetermined vacuum level move said valve to an off position.

3. A control as in claim 1, including additional means connecting said vacuum to the opposite end of said valve to act thereon and above a predetermined vacuum level move said valve to an override position blocking the flow of air and vapor through said conduit means.

4. A fuel vapor emission control for use with an internal combustion engine having an intake manifold providing a variable source of vacuum, a carburetor having a fuel-air induction passage and a throttle valve rotatably mounted therein to control flow therethrough, a fuel reservoir having a fuel vapor area therein, said emission control comprising, conduit means connecting the fuel vapors to said intake manifold, a source of air, and fuel vapor-air proportioning valve means in said conduit means controlling the mixture of and flow of fuel vapor and air therethrough to said manifold,said valve means comprising a valve body slidably containing a spool valve movable to a plurality of positions and having a plurality of axially spaced interconnected lands, said valve body having an air inlet connected to said source of air and an outlet spaced therefrom, and a fuel vapor inlet and an outlet spaced therefrom, means joining said outlets, said valve in a first position connecting said inlets to their respective outlets and in the remaining of said plurality of positions blocking the connection between said inlets and outlets, means biasing said valve to a blocking position, and means connecting said fuel vapor to act on said valve and move the same to said first position above a predetermined vapor pressure level.

5. A control as in claim 4, including connecting means connecting said valve to said vacuum whereby said valve is acted upon and moved by said vacuum to a blocking position above a predetermined vacuum level.

6. A control as in claim 5, said connecting means connecting said valve to the vacuum in said induction passage at a point slightly below the throttle valve.

7. A control as in claim 6, including a plurality of flow restricting means proportioning the flow of air and fuel vapor to the respective valve body inlets. 

2. A control as in claim 1, including additional means connecting said vacuum to said valve to act thereon and above a predetermined vacuum level move said valve to an off position.
 3. A control as in claim 1, including additional means connecting said vacuum to the opposite end of said valve to act thereon and above a predetermined vacuum level move said valve to an override position blocking the flow of air and vapor through said conduit means.
 4. A fuel vapor emission control for use with an internal combustion engine having an intake manifold providing a variable source of vacuum, a carburetor having a fuel-air induction passage and a throttle valve rotatably mounted therein to control flow therethrough, a fuel reservoir having a fuel vapor area therein, said emission control comprising, conduit means connecting the fuel vapors to said intake manifold, a source of air, and fuel vapor-air propOrtioning valve means in said conduit means controlling the mixture of and flow of fuel vapor and air therethrough to said manifold, said valve means comprising a valve body slidably containing a spool valve movable to a plurality of positions and having a plurality of axially spaced interconnected lands, said valve body having an air inlet connected to said source of air and an outlet spaced therefrom, and a fuel vapor inlet and an outlet spaced therefrom, means joining said outlets, said valve in a first position connecting said inlets to their respective outlets and in the remaining of said plurality of positions blocking the connection between said inlets and outlets, means biasing said valve to a blocking position, and means connecting said fuel vapor to act on said valve and move the same to said first position above a predetermined vapor pressure level.
 5. A control as in claim 4, including connecting means connecting said valve to said vacuum whereby said valve is acted upon and moved by said vacuum to a blocking position above a predetermined vacuum level.
 6. A control as in claim 5, said connecting means connecting said valve to the vacuum in said induction passage at a point slightly below the throttle valve.
 7. A control as in claim 6, including a plurality of flow restricting means proportioning the flow of air and fuel vapor to the respective valve body inlets. 